What is the standard of review for judicial review of administrative decisions?

In Ryan v. Law Society (New Brunswick), [2003] S.C.C. 20, Iacobucci J., for the court, wrote that there were only three standards for judicial review of administrative decisions, namely, correctness, reasonableness and patent unreasonableness. As well, he wrote that the pragmatic and functional approach should be adopted to determine the level of deference. At para. 27 he wrote: 27. The pragmatic and functional approach determines the standard of review in relation to four contextual factors: (1) the presence or absence of a privative clause or statutory right of appeal; (2) the expertise of the tribunal relative to that of the reviewing court on the issue in question; (3) the purposes of the legislation and the provision in particular; and (4) the nature of the question -- law, fact, or mixed law and fact.